Assembling work by a robot has been widely adopted, and most robots have a position and posture instructed in advance and perform repetitive work according to the instruction. In recent years, there has been a demand for more advanced work such as fitting one part to another. As disclosed in International Publication NO. WO98/017444, there is known a force control robot system which uses workpiece position detection by a visual sensor and force control by a force sensor. This system includes, as illustrated in FIG. 4, a force sensor 103 and a hand 104 mounted on a finger section 102 of a robot 101, a controller 105 for controlling the robot 101, etc., and fits a first part 107 held by a holding claw of a hand 104 into a second part 108. The second part 108 is positioned by a positioning device 109, and a visual sensor 110 for detecting the positions and postures of the first part 107 and the second part 108 is fixed to a surface plate 111.
The force control robot system includes a hand for holding a first part, a robot including a force sensor for detecting force applied to the first part, a visual sensor for obtaining image data to obtain a positional relationship between the first part and a second part, and a control unit for controlling the robot and the visual sensor. The control unit includes a fitting operation performing unit for moving the first part held by the hand of the robot close to the second part and performing fitting operation under force control based on an output of the force sensor. The control unit also includes a correcting unit for obtaining workpiece position data representing a positional relationship between the first part and the second part based on image data obtained by the visual sensor, and for correcting the position and posture of the robot based on the obtained workpiece position data, in advance of the fitting operation. Further, the control unit includes a discriminating unit for obtaining data representing a fitting state of the first part in the second part based on image data of the first part and the second part obtained by the visual sensor, and for discriminating whether or not the parts are in a properly fitted state based on the obtained fitting state data, after completing the fitting operation.
Dual arm robots with two arms are also beginning to be introduced to production sites. As disclosed in Japanese Patent Application Laid-Open No. 2008-168406, a workpiece mounting system is known in which a dual arm robot can hold two workpieces and mount one workpiece on another with high precision.